Butterflies in the Brecon Beacons National Park

The Brecon Beacons National Park is home to rare butterflies, the marsh fritillary and the brown hairstreak.

Marsh fritillaries

An attractive butterfly checked orange, brown and cream, the marsh fritillary is now very scarce in the UK. Some of the strongest remaining populations occur on the grasslands of South Wales. One of these key areas is around Penderyn in the south of our National Park.

The marsh fritillary population fluctuates – they may be abundant on a site for some years but a few years later there will be very few. They require areas of damp grassland that have not been grazed too short, with tussocks of grasses, reeds and devil’s bit scabious, to provide food for the caterpillars. Adults move from site to site to seek suitable grasslands and avoid predators.

Brown hairstreaks

The brown hairstreak is a butterfly that was once common across the UK but is now scarce. There are few sites for them within the National Park. The caterpillars feed on blackthorn and the availability of this plant has a direct impact on how numerous or widespread the butterflies are. Despite blackthorn being very common, brown hairstreaks have declined because of the way hedges are managed. In winter, the adult lays its eggs on the soft new shoots of blackthorn and these eggs then hatch in the spring. Unfortunately, the blackthorn in hedges is often cut every year and the eggs are destroyed by the hedge cutters.